The invention relates to a means and method of preventing unauthorized access of personnel into the hoistway of an elevator system. In particular the invention provides a specific landing door lock with an auxiliary release mechanism which can only be actuated during maintenance or emergency conditions hereinafter referred to as abnormal operating conditions.
In modern elevator systems it is common practice to provide a lock on each landing door of an elevator system. The lock has two specific mechanisms that are employed to unlock the landing door. The first is the main release mechanism which is actuated during normal operating conditions of the elevator by a retractable cam mounted either on a car of the elevator or on the landing door. Accordingly, when the car reaches the desired floor, the main release mechanism is actuated on the neighboring landing door thereby enabling transferal of passengers between the car and the floor. Naturally there are occasions (during maintenance or emergency conditions for example) when it is necessary for authorized personnel to gain direct access to the hoistway from a floor. For this purpose the lock further includes an auxiliary release mechanism. Generally, the auxiliary release mechanism is actuated manually by an appropriate key in the possession of the service engineer or firefighter (authorized personnel) and the landing door can then be opened manually. It has become apparent that this security precaution is no longer adequate to prevent unauthorized personnel such as vandals from opening the landing door and causing damage to elevator equipment as well as endangering their own safety.
To ensure ease of use and universal applicability for all elevator systems within a particular region or area, the key for the auxiliary locking mechanisms is typically of a simple design. For example in Europe, the relevant standard, EN 81-1:1998, specifies that the key will fit an unlocking triangle which is accessible from the landing. The unlocking triangle is shaped as a solid equilateral triangle with rounded corners. A person who is determined to enter the hoistway can easily replicate a key that will fit the unlocking triangle. Occasionally, the unlocking triangle may be covered with a screw cap or plug however these are not particularly effective deterrents and do not prevent deliberate misuse.
In the United States of America it is common practice to supply an unlocking key with a semicircular profile which fits into a corresponding keyhole accessible from the landing. Instead of rotating the key, it is moved to one side which action slides an unlocking lever in the opposite direction to actuate the auxiliary release mechanism. Again, this relatively simple arrangement is no longer effective in preventing deliberate misuse.
A solution to the problem was proposed in GB 1498039. Instead of key activation, the auxiliary release mechanism of GB 1498039 is connected electrically to a manually operable switch, activation of which releases the landing door. The switch can be housed in a locked compartment in the elevator car, on the landing or in the machine room of the elevator system.
The switch, being a dedicated component to the elevator system, must always be available on site and therefore there is always an inherent risk of vandalism leading to unauthorized access to the hoistway. Furthermore, the continual pressure to reduce space consumption within the industry has led to the design of modern systems that do not have a machine room, the machine being mounted instead in the hoistway. In these installations the locked compartment must be mounted either in the car or landing, both of which are generally accessible to the public, thereby increasing the risk of vandalism and unauthorized access.
If the mechanism of GB 1498039 is to comply with the standards, the compartment containing the release switch must be capable of being unlocked using a standard key. In this instance the mechanism is no better at preventing unauthorized access than the existing key actuated release mechanism; a person merely has the additional task of manually activating the switch to open the landing doors.
In JP 08 059151 a similar arrangement is described where a manual switch is provided in the elevator car and another manual switch is provided in the control room. Only when both switches have been activated can the landing door be opened.
JP 2000072361 shows an arrangement whereby a shutter blocks the keyhole on a landing door at all times except when the car is in a docking position directly opposite the landing door. It is apparent that if this system is used, then no access is possible to the hoistway for maintenance purposes.
An alternative solution has been proposed in GB 1511838. In this solution the landing door lock includes at least one fixed obstruction intended to prevent objects other than the appropriate key from being inserted through the keyhole and actuating the auxiliary release mechanism. All objects, including the key, are prevented from being inserted along a direct path through the keyhole. Instead, the key is inserted along a non-direct path to avoid a projection provided in the keyhole. When fully inserted, an aperture in the key can accommodate the projection and therefore the key can be levered to actuate the auxiliary release mechanism.
Again the solution does not prevent the would-be vandal from attempting to gain access to the hoistway, an act which itself may be extremely hazardous as a makeshift replica key could become securely lodged in the keyhole preventing subsequent operation by authorized personnel, particularly during emergency procedures.